Message Forwarding Method, System, and Relay Agent Device

1. A method for forwarding message, comprising: receiving, by a relay agent device, a first dynamic host configuration protocol (DHCP) for Internet Protocol (IP) version 6 (DHCPv6) packet from a user device through an interface on the relay agent device; generating, by the relay agent device, a relay-forward message comprising a relay-message option, a first interface-identifier (ID) option and a second interface-ID option, wherein both the first interface-ID option and the second interface-ID option are in compliance to option 18 defined in request for comments (RFC) 3315, wherein the relay-message option encapsulates the first DHCPv6 packet, wherein the first interface-ID option indicates an ID of a port on the relay agent device on which the first DHCPv6 packet is received, and wherein the second interface-ID option indicates an ID of the interface on which the first DHCPv6 packet is received; and sending, by the relay agent device, the relay-forward message to a DHCPv6 server.

2. The method according to claim 1 , further comprising: receiving, by the relay agent device, a relay-reply message from network side, wherein the relay-reply message encapsulates a second DHCPv6 packet and the ID of the interface; and forwarding, by the relay agent device, the second DHCPv6 packet to the user device according to the ID of the interface.

3. The method according to claim 1 , wherein the relay agent device comprises an access node.

4. A relay agent device, comprising: a non-transitory computer-readable storage medium; and a processor coupled to the non-transitory computer-readable storage medium and configured to execute instructions stored in the non-transitory computer-readable storage medium to perform the following functions: receive a dynamic host configuration protocol (DHCP) for Internet Protocol (IP) version 6 (DHCPv6) packet from a user device; generate a relay-forward message comprising a first interface-identifier (ID) option and a second interface-ID option, wherein the first interface-ID option and the second interface-ID option are option 18 defined in request for comments (RFC) 3315, wherein the first interface-ID option indicates an ID of a port on the relay agent device on which the first DHCPv6 packet is received, and wherein the second interface-ID option indicates an ID of the interface on which the first DHCPv6 packet is received; and send the relay-forward message.

5. The relay agent device according to claim 4 , further comprising an access node.

6. A system for forwarding message, comprising: a relay agent device; and a user device, wherein the user device is configured to transmit a dynamic host configuration protocol (DHCP) for Internet Protocol (IP) version 6 (DHCPv6) packet to the relay agent device, wherein the relay agent device is configured to: receive the DHCPv6 packet through an interface; generate a relay-forward message comprising a relay-message option, a first interface-identifier (ID) option and a second interface-ID option, wherein both the first interface-ID option and the second interface-ID option are option 18 defined in request for comments (RFC) 3315, wherein the relay-message option encapsulates the first DHCPv6 packet, wherein the first interface-ID option indicates an ID of a port on the relay agent device on which the first DHCPv6 packet was received, and wherein the second interface-ID option indicates an ID of the interface on which the first DHCPv6 packet is received; and send the relay-forward message.

7. The system according to claim 6 , wherein the relay agent device comprises an access node.

8. The system according to claim 6 , wherein the user device comprises a DHCPv6 client.